Centrifugal fan and impeller thereof

ABSTRACT

A centrifugal fan includes a housing defining an inner space therein and an impeller rotatably received in the inner space of the housing. The impeller includes a hub, a blade ring surrounding the hub, a plurality of first blades extending from the hub to the blade ring, and a plurality of second blades extending from the blade ring. Each first blade includes an inner portion between the hub and the blade ring, and an outer portion extending from the blade ring. The second blades and the outer portions of the first blades are arranged in alternating fashion along a circumferential direction of the blade ring. In each pair of an outer portion and an adjacent second blade, the outer portion and the second blade are curved outwards away from each other toward substantially opposite directions.

BACKGROUND

1. Technical Field

The present disclosure relates generally to centrifugal fans, and more particularly to an impeller of a centrifugal fan.

2. Description of Related Art

Generally, cooling fans are used in combination with heat sinks for cooling electronic components, such as CPUs. Most portable electronic systems that contain electronic components, such as laptop computers and notebook computers, have limited space therein. Thus a centrifugal fan which requires only a small space for installation is generally used in such electronic systems.

In use of the centrifugal fan, an impeller of the centrifugal fan rotates to generate an airflow to the electronic component, and thereby continuously take away heat of the electronic component. In order to improve the cooling and heat dissipation efficiency, the most direct and effective way is to increase the revolving speed of the impeller, thereby increasing the flow rate of the airflow. However, increasing the revolving speed of the impeller generally causes a noise level generated by the centrifugal fan to also be increased. This may annoy or cause discomfort to a user near the centrifugal fan.

What is needed, therefore, is a centrifugal fan with an improved impeller to overcome the above-described limitations.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an isometric, assembled view of a centrifugal fan, according to an exemplary embodiment.

FIG. 2 is an exploded view of FIG. 1.

FIG. 3 is an enlarged view of an impeller of the centrifugal fan shown in FIG. 2.

DETAILED DESCRIPTION

Referring to FIG. 1, a centrifugal fan according to an exemplary embodiment is shown. The centrifugal fan includes a housing 12 and an impeller 14 rotatably received in the housing 12.

Referring also to FIG. 2, the housing 12 includes a top cover 120, a bottom cover 122, and a sidewall 124 interconnecting outer peripheries of the top cover 120 and the bottom cover 122. The top cover 120, the bottom cover 122 and the sidewall 124 cooperatively define an inner space 126 for receiving the impeller 14 therein. In this embodiment, the sidewall 124 is integrally formed with the top cover 120. A first air inlet 121 is defined in a central portion of the top cover 120, and a second air inlet 123 is defined in a central portion of the bottom cover 122. The first air inlet 121 and the second air inlet 123 are coaxial. An air outlet 131 is defined in the sidewall 124 of the housing 12, and is oriented perpendicular to the first air inlet 121 and the second air inlet 123.

A circular supporting base 127 is arranged in a central portion of the second air inlet 123 of the bottom cover 122. A plurality of ribs 128 extend outwards from the supporting base 127 to connect an inner periphery of the bottom cover 122, thus fixing the supporting base 127 to the bottom cover 122. A tube 129 extends perpendicularly from a central portion of the supporting base 127 towards the top cover 120. A bearing 130 is received in the tube 129 for supporting rotation of the impeller 14.

Referring also to FIG. 3, the impeller 14 includes a hub 140, a blade ring 144, a plurality of first blades 142, and a plurality of second blades 146. In this embodiment, the blade ring 144, the first blades 142, the second blades 146 and the hub 140 are integrally formed by an injection molding process as a single monolithic piece. The hub 140 includes a circular wall 141, and an annular wall 143 extending perpendicularly downward from a periphery of the circular wall 141. The blade ring 144 surrounds and is spaced from the annular wall 143 of the hub 140. A bottom side of the annular wall 143 is substantially coplanar with the blade ring 144.

The first blades 142 extend outwards from an outer circumferential surface of the annular wall 143 of the hub 140 to the blade ring 144, and are evenly arranged along a circumferential direction of the annular wall 143. Each first blade 142 includes a straight inner portion 145 and a curved outer portion 147. The inner portion 145 extends from an outer circumferential surface of the annular wall 143 of the hub 140 to an inner edge of blade ring 144, while the outer portion 147 extends outwards from the inner portion 145 to an outer edge of the blade ring 144. That is, the inner portions 145 of the first blades 142 are located between the annular wall 143 and the blade ring 144, while the outer portions 147 are entirely arranged on the blade ring 144 with bottom sides thereof integrally joined with a top side of the blade ring 144.

The second blades 146 are evenly arranged along a circumferential direction of the blade ring 144, with bottom sides thereof integrally joined with the top side of the blade ring 144. The second blades 146 and the outer portions 147 of the first blades 142 are arranged in an alternating fashion along a circumferential direction of the blade ring 144. Each of the second blades 146 extends curvedly from the inner edge of the blade ring 144 to the outer edge of the blade ring 144. Each of the outer portions 147 of the first blades 142 extends curvedly from the inner edge of the blade ring 144 to the outer edge of the blade ring 144. Preferably, the second blades 146 and the outer portions 147 of the first blades 142 extend curvedly such that each second blade 146 and a corresponding adjacent outer portion 147 of the first blade 142 are oriented generally symmetrically opposite each other. That is, in the present embodiment, the outer portions 147 of the first blades 142 extend outwards generally (slightly) toward a rotation direction of the impeller 14, and the second blades 146 extend outwards generally (slightly) away from the rotation direction of the impeller 14.

In this exemplary embodiment, the centrifugal fan rotates clockwise. In this example, the inner portions 145 of the first blades 142 are substantially or entirely straight, and extend aslant from the annular wall 143 generally (slightly) toward a counterclockwise direction; while the outer portions 147 of the first blades 142 are arc-shaped, and extend generally (slightly) toward a clockwise direction. Thus an area of each first blade 142 is enlarged, and more air can be driven by the first blades 142. The second blades 146 are arc-shaped, and extend generally (slightly) toward the counterclockwise direction. Considered another way, each second blade 146 and the outer portion 147 of one neighboring first blade 142 form a profile like a pair of parentheses.

Referring to FIG. 1 again, when assembled, the impeller 14 is sandwiched between the top cover 120 and the bottom cover 122, and surrounded by the sidewall 124 of the housing 12. The blade ring 144, the second blades 146 and the outer portions 147 of the first blades 142 all are located just under the top cover 120 of the housing 12, while the inner portions 145 of the first blades 142 are aligned with the first air inlet 121 and second air inlet 123. A flow channel (not shown) is defined between the sidewall 124 of the housing 12 and the outmost edges of the first blades 142 and second blades 146.

During operation, the impeller 14 is driven by a stator (not shown) of the centrifugal fan 10 to be rotatable with respect to the stator in the housing 12. As the impeller 14 rotates, the first blades 142 force the air adjacent to the first air inlet 121 and second air inlet 123 into the housing 12. The air then flows along the flow channel to the air outlet 131 to generate high-pressure airflow to the electronic component which needs to be cooled. Since the outer portions 147 of the first blades 142 are curved to enlarge the area of the first blades 142, an amount of the airflow driven by the first blades 142 is improved. Further, the second blades 146 arranged opposite to the first blades 142 can force the airflow to flow radially to the air outlet 131, to thereby reduce separation of the airflow at the outer edges of the first blades 142. Accordingly, air turbulence can be reduced, which not only reduces energy loss of the airflow, but also reduces air noise of the centrifugal fan 10. As a result, a greater amount of airflow with reduced noise, and increased speed and pressure, is generated. Thus, the heat dissipation efficiency and inconspicuousness of the centrifugal fan 10 are improved.

It is to be understood, however, that even though numerous characteristics and advantages of certain embodiments have been set forth in the foregoing description, together with details of the structures and functions of the embodiments, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the disclosure to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed. 

1. A centrifugal fan, comprising: a housing defining an inner space, an air inlet and an air outlet therein, the inner space communicating with the air inlet and air outlet, the air inlet being substantially perpendicular to the air outlet; and an impeller rotatably received in the housing, the impeller comprising a hub, a blade ring surrounding the hub, a plurality of first blades extending from the hub to the blade ring, and a plurality of second blades on the blade ring, outer portions of the first blades on the blade ring and the second blades being curved such that each second blade and a corresponding adjacent outer portion of the first blade are oriented generally symmetrically opposite each other.
 2. The centrifugal fan of claim 1, wherein the first blades and the second blades are arranged in alternating fashion along a circumferential direction of the blade ring.
 3. The centrifugal fan of claim 2, wherein the outer portions of the first blades on the blade ring are arc-shaped and the second blades are arc-shaped, each second blade and the corresponding adjacent outer portion of the first blade forming a profile of a pair of parentheses.
 4. The centrifugal fan of claim 1, wherein the outer portions of the first blades curve outwards generally toward a rotation direction of the centrifugal fan, and the second blades curve outwards generally away from the rotation direction of the centrifugal fan.
 5. The centrifugal fan of claim 4, wherein each first blade further comprises an inner portion extending from the hub to the outer portion.
 6. The centrifugal fan of claim 5, wherein the inner portion of the first blade extends outwards generally away from the rotation direction of the centrifugal fan.
 7. The centrifugal fan of claim 5, wherein the inner portion of the first blade is straight.
 8. The centrifugal fan of claim 1, wherein the housing comprises two covers arranged parallel to each other, and a sidewall interconnecting the two covers, the air inlet being defined in the two covers, the air outlet being defined in the sidewall, and wherein the blade ring, the second blades, and the outer portions of the first blades are aligned with the covers, and other portions of the first blades and the hub are aligned with the air inlet.
 9. The centrifugal fan of claim 1, wherein the hub comprises a circular wall and an annular wall extending perpendicularly from a periphery of the circular wall, an end of the annular wall farthest from the circular wall being substantially coplanar with the blade ring.
 10. An impeller, comprising: a hub comprising a circular wall and an annular wall extending from a periphery of the circular wall; a blade ring surrounding and spaced from the annular wall of the hub; a plurality of first blades extending outwards from the hub to the blade ring, each first blade comprising an inner portion between the annular wall of the hub and the blade ring, and an outer portion extending from the blade ring; and a plurality of second blades extending from the blade ring, the second blades and the outer portions of the first blades being arranged in alternating fashion along a circumferential direction of the blade ring, wherein in each pair of an outer portion and an adjacent second blade, the outer portion and the second blade are curved outwards away from each other toward substantially opposite directions.
 11. The impeller of claim 10, wherein the outer portions of the first blades and the second blades are arc-shaped, and the each pair of an outer portion and an adjacent second blade form a profile of a pair of parentheses.
 12. The impeller of claim 10, wherein the inner portion of the first blade is straight.
 13. The impeller of claim 10, wherein the blade ring is substantially coplanar with an end of the annular wall farthest from the circular wall.
 14. The impeller of claim 10, wherein the second blades and the outer portions of the first blades extend perpendicularly from the same side of the blade ring. 